Climate Alarmism: The Beginning of the End?

John reported here the other day about the leaked portion of the forthcoming report of the Intergovernmental Panel on Climate Change (IPCC) which admits the possible role of cosmic radiation in cloud formation. This may be the first time the IPCC has acknowledged this as a possible factor, even though the hypothesis has been around for more than 20 years. But the big ball game all along in climate science has been whether estimates of climate sensitivity to greenhouse gas levels would change in future IPCC reports. Here’s what I wrote about the matter in the Weekly Standard in 2010:

Eventually the climate modeling community is going to have to reconsider the central question: Have the models the IPCC uses for its predictions of catastrophic warming overestimated the climate’s sensitivity to greenhouse gases? . . . The next wave of climate revisionism is likely to reopen most of the central questions of “settled science” in the IPCC’s Working Group I.

Today Matt Ridley has a must-read article in the Wall Street Journal on this issue. He thinks the turning point has arrived. He’s been speaking with an inside reviewer, Nic Lewis, who, though prohibited from quoting from drafts-in-progress, says some of the draft material “is dynamite.” If you’re without a Journal subscription, here’s some of the key bits:

In short: We can now estimate, based on observations, how sensitive the temperature is to carbon dioxide. We do not need to rely heavily on unproven models. Comparing the trend in global temperature over the past 100-150 years with the change in “radiative forcing” (heating or cooling power) from carbon dioxide, aerosols and other sources, minus ocean heat uptake, can now give a good estimate of climate sensitivity.

The conclusion—taking the best observational estimates of the change in decadal-average global temperature between 1871-80 and 2002-11, and of the corresponding changes in forcing and ocean heat uptake—is this: A doubling of CO2 will lead to a warming of 1.6°-1.7°C (2.9°-3.1°F).

This is much lower than the IPCC’s current best estimate, 3°C (5.4°F).

Of course, Ridley warns that this may not be the lead story in the news media when the full IPCC report is issued next year:

The big question is this: Will the lead authors of the relevant chapter of the forthcoming IPCC scientific report acknowledge that the best observational evidence no longer supports the IPCC’s existing 2°-4.5°C “likely” range for climate sensitivity? Unfortunately, this seems unlikely—given the organization’s record of replacing evidence-based policy-making with policy-based evidence-making, as well as the reluctance of academic scientists to accept that what they have been maintaining for many years is wrong. . .

The scientists at the IPCC next year have to choose whether they will admit—contrary to what complex, unverifiable computer models indicate—that the observational evidence now points toward lukewarm temperature change with no net harm. On behalf of all those poor people whose lives are being ruined by high food and energy prices caused by the diversion of corn to biofuel and the subsidizing of renewable energy driven by carboncrats and their crony-capitalist friends, one can only hope the scientists will do so.

But even if the politicized scientists carry the day with the next IPCC, it will be with an air of increasing desperation and will likely receive lukewarm (pun intended) media coverage. The whole scheme is slowly unraveling. Read Ridley’s whole article if you can.

UPDATE: Nic Lewis himself has posted a detailed supplement to the Ridley article on WattsUpWithThat, complete with technical Appendices. Pour an extra large cup of coffee.